Mass transfer analysis of gas exchange through microperforated packaging films

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Viana Ramos, Andresa
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University College Cork
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The primary purpose of this work was to provide robust tools for the design of perforated packaging based on rigorous mathematical methods. A dimensionless correlation was established based on the identification of the variables affecting mass transfer through perforations. It was proved that the diameter of the perforation is the most important parameter. Air velocity and temperature (via its effect on viscosity and density of air) and diffusivity of gases through air are also relevant to this analysis. The Buckingham π Theorem was applied to identify the dimensionless numbers that provide a dimensionless correlation availing of the principle of dynamic similarity to predict the mass transfer coefficients of both oxygen and water vapour through perforations. As films tend to be much more permeable to water than to oxygen, a study on the effect of water (humidity) on films was also performed. It was found that diffusion and hence permeability can be significantly affected by the water content of the films and therefore the humidity of the atmospheres that the films are exposed to on both sides. A methodology was applied combining the William, Landel and Ferry and the Gordon-Taylor equations with the isotherm of water sorption to obtain the correct effective permeability of films during storage depending on the relative humidity. A methodology was also developed to analyse leakage flow in sealed packages in order to identify the relevant parameters that influence their variability and provide the most robust sealing conditions. The results on this thesis provide substantial data and rigorous mathematical approaches for a more efficient and accurate packaging design to achieve maximum shelf life.
Permeability , Microperforations , Mass transfer , Modified atmosphere packaging , Dimensionless correlations
Viana Ramos, A. 2017. Mass transfer analysis of gas exchange through microperforated packaging films. PhD Thesis, University College Cork.